The following relates generally to wireless communication, and more specifically to modulation spreading for wireless communications.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as a Long Term Evolution (LTE) systems or LTE-Advanced (LTE-A) systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
In some wireless communications systems, a base station may serve a large number of UEs for machine type communications (MTC). The base station and the UEs may use non-orthogonal multiple access communications, such as CDMA communications, and a grant-free transmission scheme. Although the base station may serve a large number of UEs for MTC, the base station may only be able to use a limited number of resources. Some CDMA configurations may perform well for low spectrum efficiency and lower quadrature amplitude modulation (QAM) size. However, higher order QAM schemes may utilize a larger signal-to-noise ratio (SNR) and these CDMA configurations may experience a performance drop for high spectrum efficiency and larger QAM sizes.